The invention relates to a method of and apparatus for shaping articles by the relative rolling of an active surface of a shaping tool along a shaped surface.
The most advanced methods of shaping rivet heads are based on a hypocycloidical movement of the rivet snap or die, in the course of which movement a progressive radial shifting of the material from the center of the shaped surface toward its circumference takes place. The most recent modifications of arrangements based on this principle use a superposition of two rotating motions, and also possibly of a rotating and a straight line motion, thereby extending the possibility of selection of the course of the relative rolling. Similar arrangements are also used for forging, in which one of the dies performs this motion. A common feature of all these methods is that the tool or its holder is supported by a spherical surface, the center of which is at the same time the center of the formed surface. In these cases the center of the shaping tool is in constant contact with the center of the shaped surface, and the remaining points of the active surface of the shaping tool subsequently join in the relative rolling operation. A drawback of apparatus operating with a hypocycloidical relative rolling is that the cycloids of the relative rolling follow each other in the direction of the circumference of the shaped surface, thereby generating lateral forces which act on the shaped surface. Such lateral forces may in some cases by undesirable. With known arrangements it is impossible to alter the diameter of shaping or the amplitude of the deviation within the shaping interval operations which are desirable in some cases of shaping. A drawback of known arrangements is also that important operating points which are exposed to shaping forces have to be provided with sliding frictional supports.